HardenedBSD/lib/libufs/ufs_disk_close.3
Kirk McKusick 772430dd67 Ensure I/O buffers in libufs(3) are 128-byte aligned.
Various disk controllers require their buffers to be aligned to a
cache-line size (128 bytes). For buffers allocated in structures,
ensure that they are 128-byte aligned. Use aligned_malloc to allocate
memory to ensure that the returned memory is 128-byte aligned.

While we are here, we replace the dynamically allocated inode buffer
with a buffer allocated in the uufsd structure just as the superblock
and cylinder group buffers do.

This can be removed if/when the kernel is fixed. Because this problem
has existed on one I/O subsystem or another since the 1990's, we
are probably stuck with dealing with it forever.

The problem most recent showed up in Azure, see:
    https://reviews.freebsd.org/D41728
    https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=267654
Before these fixes were applied, it was confirmed that the changes
in this commit also fixed the issue in Azure.

Reviewed-by: Warner Losh, kib
Tested-by:   Souradeep Chakrabarti of Microsoft (earlier version)
PR:          267654
Differential Revision: https://reviews.freebsd.org/D41724
2023-11-17 14:11:24 -08:00

121 lines
2.6 KiB
Groff

.\" Author: Juli Mallett <jmallett@FreeBSD.org>
.\" Date: June 04, 2003
.\" Description:
.\" Manual page for libufs functions:
.\" ufs_disk_close(3)
.\" ufs_disk_fillout(3)
.\" ufs_disk_fillout_blank(3)
.\" ufs_disk_write(3)
.\"
.\" This file is in the public domain.
.\"
.Dd November 17, 2023
.Dt UFS_DISK_CLOSE 3
.Os
.Sh NAME
.Nm ufs_disk_close ,
.Nm ufs_disk_fillout ,
.Nm ufs_disk_fillout_blank ,
.Nm ufs_disk_write
.Nd open and close userland UFS disks
.Sh LIBRARY
.Lb libufs
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.In ufs/ufs/ufsmount.h
.In ufs/ufs/dinode.h
.In ufs/ffs/fs.h
.In libufs.h
.Ft int
.Fn ufs_disk_close "struct uufsd *disk"
.Ft int
.Fn ufs_disk_fillout "struct uufsd *disk" "const char *name"
.Ft int
.Fn ufs_disk_fillout_blank "struct uufsd *disk" "const char *name"
.Ft int
.Fn ufs_disk_write "struct uufsd *disk"
.Sh DESCRIPTION
The
.Fn ufs_disk_close
function closes a disk and frees internal memory related to it.
It does not free the
.Fa disk
structure.
.Pp
The
.Fn ufs_disk_fillout
and
.Fn ufs_disk_fillout_blank
functions open a disk specified by
.Fa name
and populate the structure pointed to by
.Fa disk .
The structure referenced by the
.Fa disk
pointer must be aligned to at least the alignment specified by
.Dv LIBUFS_ALIGN
that is defined in the
.Lb libufs.h
header file.
The disk is opened read-only.
The specified
.Fa name
may be either a mountpoint, a device name or a filesystem image.
The
.Fn ufs_disk_fillout
function assumes there is a valid superblock and will fail if not,
whereas the
.Fn ufs_disk_fillout_blank
function makes no assumptions of that sort.
.Pp
The
.Fn ufs_disk_write
function attempts to re-open a disk as writable if it is not currently.
.Sh ERRORS
The function
.Fn ufs_disk_close
has no failure points.
.Pp
The function
.Fn ufs_disk_fillout
may fail for any of the reasons
.Fn ufs_disk_fillout_blank
might, as well as for any reason
.Xr sbread 3
might.
.Pp
The
.Fn ufs_disk_fillout_blank
may fail and set
.Va errno
for any of the errors specified for the library functions
.Xr open 2 ,
.Xr strdup 3 .
Additionally, it may follow the
.Xr libufs 3
error methodologies in situations where no device could be found to
open.
.Pp
The function
.Fn ufs_disk_write
may fail and set
.Va errno
for any of the errors specified for the library functions
.Xr open 2
and
.Xr stat 2 .
Namely, it will fail if the disk in question may not be written to.
.Sh SEE ALSO
.Xr open 2 ,
.Xr getfsfile 3 ,
.Xr libufs 3 ,
.Xr sbread 3
.Sh HISTORY
These functions first appeared as part of
.Xr libufs 3
in
.Fx 5.0 .
.Sh AUTHORS
.An Juli Mallett Aq Mt jmallett@FreeBSD.org